[parser] parser: add WEIGHT_STRING() function (#743)

parser/ast/functions.go

@@ -226,6 +226,7 @@ const (
 	CharLength      = "char_length"
 	CharacterLength = "character_length"
 	FindInSet       = "find_in_set"
+	WeightString    = "weight_string"
 
 	// information functions
 	Benchmark      = "benchmark"
@@ -420,6 +421,19 @@ func (n *FuncCallExpr) Restore(ctx *format.RestoreCtx) error {
 				return errors.Annotatef(err, "An error occurred while restore FuncCallExpr.Args[0]")
 			}
 		}
+	case WeightString:
+		if err := n.Args[0].Restore(ctx); err != nil {
+			return errors.Annotatef(err, "An error occurred while restore FuncCallExpr.(WEIGHT_STRING).Args[0]")
+		}
+		if len(n.Args) == 3 {
+			ctx.WriteKeyWord(" AS ")
+			ctx.WriteKeyWord(n.Args[1].(ValueExpr).GetValue().(string))
+			ctx.WritePlain("(")
+			if err := n.Args[2].Restore(ctx); err != nil {
+				return errors.Annotatef(err, "An error occurred while restore FuncCallExpr.(WEIGHT_STRING).Args[2]")
+			}
+			ctx.WritePlain(")")
+		}
 	default:
 		for i, argv := range n.Args {
 			if i != 0 {

parser/ast/functions_test.go

@@ -84,6 +84,16 @@ func (ts *testFunctionsSuite) TestFuncCallExprRestore(c *C) {
 		{"next value for sequence", "NEXTVAL(`sequence`)"},
 		{"NeXt vAluE for seQuEncE2", "NEXTVAL(`seQuEncE2`)"},
 		{"NeXt vAluE for test.seQuEncE2", "NEXTVAL(`test`.`seQuEncE2`)"},
+		{"weight_string(a)", "WEIGHT_STRING(`a`)"},
+		{"Weight_stRing(test.a)", "WEIGHT_STRING(`test`.`a`)"},
+		{"weight_string('a')", "WEIGHT_STRING('a')"},
+		// TODO(bb7133): collate for literal values cannot be restored.
+		//{"weight_string(_utf8 'a' collate utf8_general_ci)", "WEIGHT_STRING(_UTF8'a' COLLATE utf8_general_ci)"},
+		{"weight_string(_utf8 'a')", "WEIGHT_STRING(_UTF8'a')"},
+		{"weight_string(a as char(5))", "WEIGHT_STRING(`a` AS CHAR(5))"},
+		{"weight_string(a as character(5))", "WEIGHT_STRING(`a` AS CHAR(5))"},
+		{"weight_string(a as binary(5))", "WEIGHT_STRING(`a` AS BINARY(5))"},
+		{"hex(weight_string('abc' as binary(5)))", "HEX(WEIGHT_STRING('abc' AS BINARY(5)))"},
 	}
 	extractNodeFunc := func(node Node) Node {
 		return node.(*SelectStmt).Fields.Fields[0].Expr

parser/misc.go

@@ -687,6 +687,7 @@ var tokenMap = map[string]int{
 	"WARNINGS":                 warnings,
 	"ERRORS":                   identSQLErrors,
 	"WEEK":                     week,
+	"WEIGHT_STRING":            weightString,
 	"WHEN":                     when,
 	"WHERE":                    where,
 	"WIDTH":                    width,

parser/parser.y

@@ -548,6 +548,7 @@ import (
 	bindings              "BINDINGS"
 	warnings              "WARNINGS"
 	without               "WITHOUT"
+	weightString          "WEIGHT_STRING"
 	identSQLErrors        "ERRORS"
 	week                  "WEEK"
 	yearType              "YEAR"
@@ -4718,6 +4719,7 @@ UnReservedKeyword:
 |	"YEAR"
 |	"MODE"
 |	"WEEK"
+|	"WEIGHT_STRING"
 |	"ANY"
 |	"SOME"
 |	"USER"
@@ -5858,6 +5860,27 @@ FunctionCallNonKeyword:
 			Args:   []ast.ExprNode{$6, $4, direction},
 		}
 	}
+|	weightString '(' Expression ')'
+	{
+		$$ = &ast.FuncCallExpr{
+			FnName: model.NewCIStr($1),
+			Args:   []ast.ExprNode{$3},
+		}
+	}
+|	weightString '(' Expression "AS" Char FieldLen ')'
+	{
+		$$ = &ast.FuncCallExpr{
+			FnName: model.NewCIStr($1),
+			Args:   []ast.ExprNode{$3, ast.NewValueExpr("CHAR"), ast.NewValueExpr($6)},
+		}
+	}
+|	weightString '(' Expression "AS" "BINARY" FieldLen ')'
+	{
+		$$ = &ast.FuncCallExpr{
+			FnName: model.NewCIStr($1),
+			Args:   []ast.ExprNode{$3, ast.NewValueExpr("BINARY"), ast.NewValueExpr($6)},
+		}
+	}
 |	FunctionNameSequence
 
 GetFormatSelector: